In the related art, an imaging apparatus having a defect correction means is known. The defect correction means corrects a lost portion (hereinafter appropriately referred to as a “defect”) of a digital image signal associated with a pixel which does not function properly. In general, there are two types of defect correction methods, static correction and dynamic correction. The static correction is a method in which the positions of defects are stored in advance, for example, prior to the shipment of products and information of pixels around a target pixel which is to be subjected to defect correction is interpolated to obtain the information of the target pixel. The dynamic correction is a method of checking the presence of defects during the operation of an imaging apparatus and correcting the detected defect.
Moreover, there is also known an imaging apparatus having a noise reduction processing means. The noise reduction processing means reduces noise such as random noise. When line memories dedicated for the defect correction means and the noise reduction processing means are provided in the imaging apparatus, the circuit size thereof increases. Thus, the imaging apparatus may have a configuration in which the defect correction means and the noise reduction processing means share a line memory, and the results of defect correction are fed back to the noise reduction processing means. In this case, if there is an error in the defect correction by the defect correction means, since the error may affect the noise reduction on pixels other than a pixel in which erroneous defect correction was performed, the image quality may deteriorate. When the defect correction and the noise reduction processing are performed in parallel, there is a problem in that it is difficult to obtain a noise reduction effect with respect to pixels which have been subject to defect correction.
In recent years, as a countermeasure to decrease in the sensitivity due to miniaturization of pixels, many imaging apparatuses use a method of increasing the output gain of an image sensor particularly under a low illuminance condition. In an imaging apparatus, a very small leak current (dark current) generally has nearly no influence on the signal values of pixels. However, when a gain is increased, such a leak current is likely to cause a pixel to output a signal level different from the originally intended level although the difference is not as large as the extent leading to the defect. In this case, when a target pixel is subjected to defect correction, if the signal value of the target pixel is replaced with the signal level of an adjacent pixel, which is different from the originally intended level, a defect correction effect decreases.